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Couples can now choose to have a baby boy or a baby girl — at least they can with loose enough purse strings. Science Journalist Celia Spell speaks with new mom Keesa McKoy and bioethicist Dr. Steven Ralston to get the story and discuss the ethics. Listen below.

The latest controversial discovery in bat foraging

Mexican free-tailed bats congregate in the largest colonies of any mammal on earth. One colony can eat upwards of 250,000 tons of insects in one night. With such intense competition, these bats have developed a new hunting tactic: one Mexican free-tailed bat will jam the echolocation call of another in order to steal his mark.

The first bat doesn’t take this thievery lying down. He will simply jam the second bat right back, and this battle royale can continue for as many as 5 rounds. According to Aaron Corcoran, the Ph.D. student who first realized what was happening, combat ends when one bat decides it would be easier to find food elsewhere, with less competition.

Jamming works as signal scrambler. Bats scour their environment for tiny moths by sending ultrasonic waves out from their voice boxes and listening for the waves that bounce back. The returning echo strikes the sensitive inner ear receptors, creating a map of the bat’s surroundings. Jamming occurs when a call of a slightly different but very similar frequency hits the first call and forces a mistranslation. Since bat calls are frequency modulated – meaning the pitch of the calls goes up and then back down like a police siren – any noise affects it. The mistranslation happens when the second bat’s call alters the echo, causing the bat to see a different environment and ultimately miss his target.

Bat jamming is nothing new. Moths click in the direction of their incoming predator in a way that hides their location. They act as ventriloquists, essentially throwing their position to the left or to the right a few inches by sending their own frequency-modulated click. The click throws the hunter off just enough that his moth-location gauge miscalculates, preventing capture. Even human noises can jam a bat call. White noise, for instance, is a broad sound that covers a lot of frequencies. It can jam a bat as effectively as a moth. The same is true with nighttime construction sounds. The novelty of Corcoran’s discovery is that it’s the first example of jamming within the same species.

This video shows a bat closing in on his prey. The sounds you hear are the bat's echolocating calls - the way he traverses his habitat at night. The sounds have been altered so we can hear them. More videos like this one can be found on Aaron Corcoran's site.

Corcoran found these calls by accident while on a research expedition at the Southwestern Research Station in Portal, Arizona back in 2013. He left North Carolina for this sunny state to record the jamming clicks of Bertholdia trigona, also known as Grote’s tiger moth. Moth clicks and bat call frequencies sit well above those audible by people, so Corcoran used a computer program to convert the sounds. Back in the lab, he was listening to the clicks when he noticed something different about the bat calls.

“I only ever heard this new sound when a second bat was also present and making the feeding buzz sound,” said Corcoran. “I had never seen that before.”

Corcoran supported his hypothesis with more experiments and more controls out in the field. He predicted that if a recording of the new call were played, the bat in question would miss its target. He changed the speed and frequency of the signal-jamming call to show that it wasn’t just any sound throwing these bats off their game, but that particular call at that particular frequency. Only the original had an effect, and it caused the capture rate to fall from 85 percent to 15.

Not everyone is as smitten with this new discovery as Corcoran is, however. Some chiropterologists felt there wasn’t enough evidence to say the bats were in fact jamming each other.

“There’s no doubt that there are bats doing this weird behavior,” says fellow Wake Forest University Ph.D. student Nick Dowdy, who also studies bat communication. “What’s in question is the ‘why.’ The details just have not been addressed yet.”

Dowdy doesn’t question the existence of these interesting new sounds, he just doesn’t think the reasons behind them have been proven. He thinks an alternative theory proposed by Cindy Moss at Johns Hopkins University has some merit. She says the bats could just be staking their claim for a particular moth. In other words, a bat sees a plump moth flutter through his territory, so he calls dibs, expecting other bats to respect the first-come- first-serve policy. Corcoran’s so-called battles may only occur when two bats try to call dibs on the same moth. Moss doesn’t believe these bats are jamming the calls of the other, they are simply arguing over who called dibs first.

Kirsten Bohn, a behavioral biology research professor also at Johns Hopkins University, who’s been studying Mexican free-tailed bats for years, says she’s on the fence. “The only reason I would question it would be that it doesn’t seem like the biggest payoff,” she says. “It seems like it would be more prudent to go find another insect.” Emitting feeding buzzes takes so much energy that Bohn thinks that no one moth would be worth it.

Other bat researchers are also in Bohn's camp. Ela Warnecke, a psychology and Brain Science Ph.D. student at Johns Hopkins who studies bat jamming with Cindy Moss, describes bat calls as voices. She says those voices tend to be similar within the same species. “Like you and me talking right now,” she says. “We have very similar voices. If we were bats in the same room, we would change our voices. I might talk a little higher and you a little lower, so we can distinguish between the frequencies more easily.” Bats usually avoid competing with each other by altering their calls, as Warnecke describes. That’s what makes Corcoran’s finding so intriguing. The calls he detects seem to show bats competing for one prey item instead of avoiding each other.

Corcoran’s 2014 Science paper didn’t address the potential relationships between the jamming bats, which is one of Dowdy’s main concerns. The two competing bats could be mother and offspring, which would offer another explanation for the strange calls. Mother bats teach their brood how to hunt properly by accompanying them outside the cave. The calls could be a teaching tool – upping the ante for the juvenile bat and making it more difficult to find the moth.

“I should say that it is true these calls are produced when two or more bats are competing for the same food item, and it is it true that it reduces capture success,” says Dowdy. “But the headline is ‘Bats jamming Bats,’ and that’s what we don’t know for sure.

Warnecke suggests running experiments in the presence of both too much prey and too little, which would reveal whether the bats only use the call among limited resources. She says that could test the jamming idea. In the presence of ample prey bats wouldn’t need to compete or use the energy needed to emit jamming calls. The opposite would hold true in conditions of scarcity.

Corcoran says most scientists agree with his theory and think his experiments back up his findings. Dowdy, Bohn, and Warnecke are among the few who remain unconvinced. The results of Corcoran’s paper challenge previously accepted theories and facts about bats, but it also inspires discussion. This new Mexican free-tailed bat call further proves that these animals have more in their repertoire than scientists previously thought. These furry, winged creatures are complex hunters, but maybe that’s just the beginning of their intelligence.

Medical illustrator and artist Danny Quirk walked onto stage with his latest work of art trailing behind him. Quirk’s artwork stepped into the light and turned around to reveal an anatomically accurate painting of his skull bones on the back of his head.

It was HUBweek in Boston, a seven-day lecture series celebrating science, art, and culture in the greater Boston area. Quirk’s audience waited patiently in the Ether Dome at Massachusetts General Hospital to witness a “simulated” brain surgery with body painting.

Quirk used a combination of acrylic paint and latex to craft the stretchy plastic painting sheets on his model. After layering them atop his subject’s bald head behind stage, Quirk peeled off the bone-layer painting to reveal another accurate painting – this time of the brain. The effect was as if he had performed surgery on stage in front of the lecture attendees, much like doctors in the 1800s did in the Ether Dome, but without the blood. The audience loved it.

“I realized it was really needed as a great way of learning and seeing anatomy,” said Quirk, “making [the art] interactive, making it more moveable and more dimensional than a text book.”

Quirk’s signature style got started just as many original things do – by accident. It was Halloween a few years ago, and Quirk’s then-girlfriend wanted him to paint her face with the muscles underneath as part of her costume. Quirk got carried away with the accuracy of it all and discovered a talent he didn’t know he had. Now, Quirk spends a lot of his time painting models for talks at institutions like the Mayo Clinic and illustrating for medical journals such as Annals of Anatomy, and the Spine Journal.

As his style developed, Quirk began to realize the potential of body painting as an educational tool, and so did his peers. Medical students everywhere are known for cramming obscure terms into their brains right before an exam. With cadavers, illustrations, and photographs, these students created a mental muscle map, but rarely saw how these muscles moved on a living person.

University of Manchester School of Medicine graduate Meg Anderson thought the old study method was a problem, and in 2014 founded a program at the University of Edinburgh, Scotland called Art and Anatomy. She currently works as a Core Surgical Trainee at a hospital in Edinburgh.

“I found that sitting down and learning anatomy from textbooks to be quite inadequate,” said Anderson.

As a medical student, Anderson had difficulty remembering more than 206 bones and over 700 muscles in the human body. She had always liked art and found that by painting and drawing the muscles, she could remember them more easily. That is how she and her co-founder Nichola Robertson came up with their program.

Art and Anatomy Edinburgh holds anatomy courses and events throughout the year that attract medical students and the general public alike. Robertson and Anderson wanted to make anatomy fun while also supplementing the arduous task of memorizing complicated names like sternocleidomastoid.

Medical students enrolled in the Edinburgh course spend their time painting on each other. Carefully painting the inner workings of the hand on a friend in class gives students the chance to see the muscles move with their subject. It acts as a supplementary tool for more traditional methods of memorization, and medical students at the University of Edinburgh have been embracing this fun, new way of learning.

As part of this article, I decided to conduct my own body-painting experiment. I followed Quirk's technique and both designed and painted my own image -- albeit with much less skill than the artist himself.

And here is the entire process for your viewing pleasure.

Aside from medical-student learning, Meg Anderson is thinking of other ways to incorporate and use body painting. Last October, Anderson presented a project at a plastic surgeons’ meeting in Scotland that she hoped would help breast-cancer survivors understand their upcoming surgeries more completely. By painting each step of a breast reconstruction surgery on a model and photographing it for a pamphlet, Anderson helped doctors walk their patients through the process. She wanted to give breast-reconstruction patients an idea of what was about to happen without showing nervous patients gruesome photographs.

The clinical applications of body painting fed its growth over the past few years. According to Gabrielle Finn in her 2015 book Teaching Anatomy: A Practical Guide,body painting helps students comprehend the asymmetry of the human anatomy. Not every organ resides in precisely the same location in each person, and body painting can help future doctors locate the organs in different patients by forcing them to paint on people with different body shapes.

Some medical schools no longer have full cadaver dissection on the list of required classes. According to the Toronto Globe and Mail, almost half of the medical schools in Canada have removed it from their core curriculum to leave room for more specialized study and save money on cadaver preparation. Some medical schools in Illinois have made full cadaver dissection an elective. Instead, students work on individual body parts. It takes time and costs money to maintain a cadaver for an entire semester, and students are becoming increasingly pressed for time.

Anderson and Quirk do not think body painting can replace human dissection, but it can certainly help when opportunities for cadaver dissection become limited. Incorporating kinesthetic and visual learning keeps medical students stimulated, which is shown through Art and Anatomy’s full courses. Demand for supplementary teaching methods is high, and body painting fits in with that need.

The staff at Art and Anatomy also encourage younger students to take part in body painting as part of public engagement. This past Halloween, artists at the Surgeons’ Hall Museum in Edinburgh painted anyone who was willing to be a model.

“I’m not from a medical family,” Anderson said. “So I would have absolutely loved some exposure to something like this as a kid.”

Quirk and Anderson both want to make anatomy more accessible to the public and attempt to do so through art.

“You can peel away the layers and see how those muscles work on a moving, breathing body,” says Quirk, and he thinks that makes all the difference when engaging students.

Jackie Novak and Claudia Bentley sit across from me, poised to play my game.

Jackie’s straight blonde hair sits above her shoulders showcasing her large, silver earrings. Claudia’s dark-rimmed glasses frame her face, and her bright red and green Christmas jewelry pops against the stark black and white stripes of her sweater. With Santa’s sleigh wrapped around her neck, tiny snowmen swaying from her wrist, and Rudolph dangling from her ears, Claudia is ready for the season. Jackie reaches up to tuck a loose strand of hair behind her ear in a fashion eerily similar to Claudia’s.

I enlisted these 63-year-old identical twins as a part of my own informal experiment. I was following the lead of a new study from the October issue of Cell. Professor Jeremy Wilmer of Wellesley University and post-doctoral fellow Laura Germine of Massachusetts General Hospital had set out to study beauty preferences between twins. They found, surprisingly, that the age-old adage may be true: beauty is in the eye of the beholder, even for two people who share 100% of their genes.

Researchers and philosophers alike have tried to understand beauty: what makes an object or person appealing to another. Wilmer and Germine found that half of everyone’s preferences are shared, and half are individual — placing more emphasis on personal experiences and opinions on attractiveness than originally thought.

For the Cell study, identical twin participants took surveys and tests on Germine’s brain game website, looking at different computer-generated faces and rating their attractiveness. My casual experiment mimicked the researchers’, but instead of using a program to create people, I made the faces more recognizable. Jackie and Claudia were forced to choose between celebrities.

They agreed on the male actors – their decisions so quick they sounded almost rehearsed. George Clooney outdid Johnny Depp, and John Stamos beat Jake Gyllenhaal. But when asked to pick actresses, Claudia and Jackie weren’t so agreeable. Jackie thought Meryl Streep was a classic beauty, but Claudia preferred Farrah Faucett and said she was more of bombshell. Jackie also chose Kate Winslet over Rachel McAdams, but Claudia disagreed.

Scientists love to question nature versus nurture, and studies like mine – well, the more scientific versions – add fodder to the idea that decisions of attraction are all our own.

“Different people have different tastes and different preferences,” says Wilmer. “People, even twins, go out and search for different things.”

So the rules of attraction are more than just genetics. Wilmer says our personal experiences play a large role in what and whom we find beautiful. Every unique experience contributes to people’s preferences. Every face you see on your morning commute, on your evening run, and even while scrolling through your social media feeds subtly affects you and your choices.

Another interesting finding of the Cell paper is that the more average the face, the more attractive it is. Wilmer and Germine’s team used a morphing program to blend the faces together in their study. Participants picked the blended face every time.

“Familiarity drives the averageness preference over time,” says Germine. This familiarity stems from all the faces you come across throughout the day. People are more likely to find particular faces attractive if they feel at ease, if they recognize the look. That’s how twins can differ so much. Rachel McAdams’ look may have been more prevalent in Claudia’s daily life and Kate Winslet’s look in Jackie’s. The subtle differences are the important ones.

But not everyone can focus on unique preferences. Ad campaigns and film directors want to appeal to the average shopper, and to do so, they use the average face. Carolyn Clark is an advertising professor at Boston University, and she has held senior positions at multiple advertising agencies. She says it’s important to focus on the faces that the general population agrees are attractive.

“I can’t send you a private message while also appealing to a large group of people,” she says. “The target for an ad is never just one person.”

Understanding beauty perception is also important for you and me. We date, we get married, or we stay single. We find particular people cute, hot, beautiful, or handsome. But getting to the bottom of who, why, and how is the role of “neuroaesthetics,” an emerging realm of study devoted to the brain’s interpretation and reaction to beauty.

“The aesthetic” was a term coined by philosophers as a way to look at regular objects – they believed there was a specific region in the brain devoted to interpreting beauty in art and people. Neuroaesthetics emerges from this idea. Scientists want to locate the brain area in charge of determining beauty and discover the physiological basis for Claudia and Jackie’s difference of opinion.

Steven Brown, a neuroscience professor at McMaster University in Ontario, is one of those scientists. Brown and his team examined the brain’s reaction to aesthetically pleasing paintings and objects in over 90 other neuroimaging studies. As it turns out, a small portion of the brain found in the deep recesses of the cerebral cortex perceives beauty. It’s called the anterior insula, and it’s the same area that processes pain and disgust. And it does so differently in each person even if they are identical twins.

Brown’s interpretation: the anterior insula is merely determining how useful something might be, whether it be a flower, painting, or potential mate. Food, for example, is appealing when you’re hungry, but not when you’re feeling ill. The anterior insula determines which of those reactions is right for you. It’s a basic to-eat-or-not-to-eat question, and hot-or-not falls under that same job description.

Bronstad and Russell separated their participants into siblings, spouses, friends, and strangers. Previous papers show that people across cultures can agree on attractive faces, but people within the same or similar culture tend to agree more often. By segregating study participants, the researchers determined that beauty is in fact a social construct, determined by your surroundings. Results showed that spouses agreed on attractiveness most often, followed by siblings, friends, and then strangers. The differences between spouses, siblings, and friends, was not statistically significant.

“Every time they walk down the street, they’re looking at different faces,” says Wilmer. “Take a whole lifetime of that, and that can really add up.”

Without caller ID, Claudia and Jackie’s family have a hard time distinguishing them over the phone. Their own dad used each twin’s personal greeting to sort them out. Claudia always started her calls with “Hey, Daddy,” and Jackie began with “Hey, Pop.” Genetics may determine the sound of their voices, but personality rings true in the end.

Different experiences distinguish our opinions and perceptions. Claudia and Jackie are just another example of that.